Using the idea of a mist lift cycle to generate power differs in many aspects from traditional open cycle OTEC systems. In a mist lift system, the entire mass of seawater is used to generate electricity, rather than just the low density flash-evaporated vapor. This avoids the need for large, expensive water vapor turbines.
The concepts behind the standard mist lift technology, an alternative to traditional open cycle OTEC systems, is described in U.S. Pat. Nos. 4,441,321 and 4,216,657, the entire contents of which are hereby incorporated by reference for background on the technology. The mist lift cycle is designed to generate power using a fine mixture of water vapor and droplets at the bottom of a chamber, where the vapor is cooled and condensed at the upper portion of the chamber to create a lower pressure region. A rush of the water vapor toward the cooler and lower pressure area drags water droplets toward the top of the chamber. In this manner, mass is moved from the bottom to the top, driven by the temperature and pressure differential. Once the water is elevated, now condensed, it passes through a water turbine coupled to a generator to produce electricity.
Despite the benefits that the mist lift design provides over previous OTEC systems, the original implementation of mist lift left unsolved environmental and physical challenges. For example, variations in wave-induced motions can cause disturbances in the pitch and/or roll of a floating structure, and changes in surface seawater temperatures can affect the thermodynamics of the system. These are variables that could impact the ability of a mist lift system to efficiently generate power.